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1.
ACS Nano ; 2024 May 19.
Artículo en Inglés | MEDLINE | ID: mdl-38764189

RESUMEN

Ferroelasticity is a phenomenon in which a material exhibits two or more equally stable orientation variants and can be switched from one form to another under an applied stress. Recent works have demonstrated that two-dimensional layered organic-inorganic hybrid Ruddlesden-Popper perovskites can serve as ideal platforms for realizing ferroelasticity, however, the ferroelastic (FE) behavior of structures with a single octahedra layer such as (BA)2PbI4 [BA = CH3(CH2)3NH3+] has remained elusive. Herein, by using a combined first-principles and metadynamics approach, the FE behavior of (BA)2PbI4 under mechanical and thermal stresses is uncovered. FE switching is mediated by cross-plane intermolecular coupling, which could occur through multiple rotational modes, rendering the formation of FE domains and several metastable paraelastic (PE) phases. Such metastable phases are akin to wrinkled structures in other layered materials and can act as a "funnel" of hole carriers. Thermal excitation tends to flatten the kinetic barriers of the transition pathways between orientation variants, suggesting an enhanced concentration of metastable PE states at high temperatures, while halogen mixing with Br raises these barriers and conversely lowers the concentration of PE states. These findings reveal the rich structural diversity of (BA)2PbI4 domains, which can play a vital role in enhancing the optoelectronic properties of the perovskite and raise exciting prospects for mechanical switching, shape memory, and information processing.

2.
Adv Sci (Weinh) ; : e2307995, 2024 Mar 11.
Artículo en Inglés | MEDLINE | ID: mdl-38468444

RESUMEN

Heterogeneous structures and doping strategies have been intensively used to manipulate the catalytic conversion of polysulfides to enhance reaction kinetics and suppress the shuttle effect in lithium-sulfur (Li-S) batteries. However, understanding how to select suitable strategies for engineering the electronic structure of polar catalysts is lacking. Here, a comparative investigation between heterogeneous structures and doping strategies is conducted to assess their impact on the modulation of the electronic structures and their effectiveness in catalyzing the conversion of polysulfides. These findings reveal that Co0.125 Zn0.875 Se, with metal-cation dopants, exhibits superior performance compared to CoSe2 /ZnSe heterogeneous structures. The incorporation of low Co2+ dopants induces the subtle lattice strain in Co0.125 Zn0.875 Se, resulting in the increased exposure of active sites. As a result, Co0.125 Zn0.875 Se demonstrates enhanced electron accumulation on surface Se sites, improved charge carrier mobility, and optimized both p-band and d-band centers. The Li-S cells employing Co0.125 Zn0.875 Se catalyst demonstrate significantly improved capacity (1261.3 mAh g-1 at 0.5 C) and cycle stability (0.048% capacity delay rate within 1000 cycles at 2 C). This study provides valuable guidance for the modulation of the electronic structure of typical polar catalysts, serving as a design directive to tailor the catalytic activity of advanced Li-S catalysts.

3.
J Phys Chem Lett ; 15(2): 575-582, 2024 Jan 18.
Artículo en Inglés | MEDLINE | ID: mdl-38198562

RESUMEN

Water is often viewed as detrimental to organic halide perovskite stability. However, evidence highlights its efficacy as a solvent during organic perovskite liquid synthesis. This paradox prompts an investigation into water's influence on perovskite nanoclusters. Employing first principle calculations and ab initio molecular dynamics simulations, surprisingly, we discover some subsurface layers of methylammonium lead iodide (MAPbI3) nanoclusters exhibit stronger relaxation than surface layers. Moreover, a strong quantum confinement effect enhances the band gap of MAPbI3 as the nanocluster size decreases. Notably, the water molecules above MAPbI3 nanoclusters induce rich localized defect states, generating low-lying shallow states above the valence band for the small amounts of surface water molecules and band-like deep states across the whole gap for large nanoclusters. This work provides insights into water's role in the electronic structure and structural evolution of perovskite nanoclusters, aiding the design of water-resistant layers to protect perovskite quantum dots from ambient humidity.

4.
Natl Sci Rev ; 11(2): nwad066, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38213518

RESUMEN

We review recent progress in the electronic structure study of intrinsic magnetic topological insulators (MnBi2Te4) · (Bi2Te3)n ([Formula: see text]) family. Specifically, we focus on the ubiquitously (nearly) gapless behavior of the topological Dirac surface state observed by photoemission spectroscopy, even though a large Dirac gap is expected because of surface ferromagnetic order. The dichotomy between experiment and theory concerning this gap behavior is perhaps the most critical and puzzling question in this frontier. We discuss various proposals accounting for the lack of magnetic effect on the topological Dirac surface state, which are mainly categorized into two pictures, magnetic reconfiguration and topological surface state redistribution. Band engineering towards opening a magnetic gap of topological surface states provides great opportunities to realize quantized topological transport and axion electrodynamics at higher temperatures.

5.
Proc Natl Acad Sci U S A ; 120(43): e2219491120, 2023 Oct 24.
Artículo en Inglés | MEDLINE | ID: mdl-37851678

RESUMEN

In conventional superconductors, electron-phonon coupling plays a dominant role in generating superconductivity. In high-temperature cuprate superconductors, the existence of electron coupling with phonons and other boson modes and its role in producing high-temperature superconductivity remain unclear. The evidence of electron-boson coupling mainly comes from angle-resolved photoemission (ARPES) observations of [Formula: see text]70-meV nodal dispersion kink and [Formula: see text]40-meV antinodal kink. However, the reported results are sporadic and the nature of the involved bosons is still under debate. Here we report findings of ubiquitous two coexisting electron-mode couplings in cuprate superconductors. By taking ultrahigh-resolution laser-based ARPES measurements, we found that the electrons are coupled simultaneously with two sharp modes at [Formula: see text]70meV and [Formula: see text]40meV in different superconductors with different dopings, over the entire momentum space and at different temperatures above and below the superconducting transition temperature. These observations favor phonons as the origin of the modes coupled with electrons and the observed electron-mode couplings are unusual because the associated energy scales do not exhibit an obvious energy shift across the superconducting transition. We further find that the well-known "peak-dip-hump" structure, which has long been considered a hallmark of superconductivity, is also omnipresent and consists of "peak-double dip-double hump" finer structures that originate from electron coupling with two sharp modes. These results provide a unified picture for the [Formula: see text]70-meV and [Formula: see text]40-meV energy scales and their evolutions with momentum, doping and temperature. They provide key information to understand the origin of these energy scales and their role in generating anomalous normal state and high-temperature superconductivity.

6.
J Inflamm Res ; 16: 4503-4526, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37854313

RESUMEN

Hyperoside is a flavonol glycoside mainly found in plants of the genera Hypericum and Crataegus, and also detected in many plant species such as Abelmoschus manihot, Ribes nigrum, Rosa rugosa, Agrostis stolonifera, Apocynum venetum and Nelumbo nucifera. This compound exhibits a multitude of biological functions including anti-inflammatory, antidepressant, antioxidative, vascular protective effects and neuroprotective effects, etc. This review summarizes the quantification, original plant, chemical structure and property, structure-activity relationship, pharmacologic effect, pharmacokinetics, toxicity and clinical application of hyperoside, which will be significant for the exploitation for new drug and full utilization of this compound.

7.
ACS Nano ; 17(17): 16530-16538, 2023 Sep 12.
Artículo en Inglés | MEDLINE | ID: mdl-37646299

RESUMEN

As a prototype of the Weyl superconductor, layered molybdenum ditelluride (MoTe2) encompasses two semimetallic phases (1T' and Td) which differentiate from each other via a slight tilting of the out-of-plane lattice. Both phases are subjected to serious phase mixing, which complicates the analysis of its origin of superconductivity. Herein, we explore the electron-phonon coupling (EPC) of the monolayer semimetallic MoTe2, without phase ambiguity under this thickness limit. Apart from the hardening or softening of the phonon modes, the strength of the EPC can be strongly modulated by doping. Specifically, longitudinal and out-of-plane acoustic modes are significantly activated for electron doped MoTe2. This is ascribed to the presence of rich valley states and equispaced nesting bands, which are dynamically populated under charge doping. Through comparing the monolayer and bilayer MoTe2, the strength of EPC is found to be less likely to depend on thickness for neutral samples but clearly promoted for thinner samples with electron doping, while for hole doping, the strength alters more significantly with the thickness than doping. Our work explains the issue of the doping sensitivity of the superconductivity in semimetallic MoTe2 and establishes the critical role of activating acoustic phonons in such low-dimensional materials.

8.
Nat Nanotechnol ; 18(12): 1401-1408, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37653051

RESUMEN

Patterning antidots, which are regions of potential hills that repel electrons, into well-defined antidot lattices creates fascinating artificial periodic structures, leading to anomalous transport properties and exotic quantum phenomena in two-dimensional systems. Although nanolithography has brought conventional antidots from the semiclassical regime to the quantum regime, achieving precise control over the size of each antidot and its spatial period at the atomic scale has remained challenging. However, attaining such control opens the door to a new paradigm, enabling the creation of quantum antidots with discrete quantum hole states, which, in turn, offer a fertile platform to explore novel quantum phenomena and hot electron dynamics in previously inaccessible regimes. Here we report an atomically precise bottom-up fabrication of a series of atomic-scale quantum antidots through a thermal-induced assembly of a chalcogenide single vacancy in PtTe2. Such quantum antidots consist of highly ordered single-vacancy lattices, spaced by a single Te atom, reaching the ultimate downscaling limit of antidot lattices. Increasing the number of single vacancies in quantum antidots strengthens the cumulative repulsive potential and consequently enhances the collective interference of multiple-pocket scattered quasiparticles inside quantum antidots, creating multilevel quantum hole states with a tunable gap from the telecom to far-infrared regime. Moreover, precisely engineered quantum hole states of quantum antidots are geometry protected and thus survive on oxygen substitutional doping. Therefore, single-vacancy-assembled quantum antidots exhibit unprecedented robustness and property tunability, positioning them as highly promising candidates for advancing quantum information and photocatalysis technologies.

9.
ACS Appl Mater Interfaces ; 15(27): 32475-32486, 2023 Jul 12.
Artículo en Inglés | MEDLINE | ID: mdl-37386799

RESUMEN

Solvent engineering is highly essential for the upscaling synthesis of high-quality metal halide perovskite materials for solar cells. The complexity in the colloidal containing various residual species poses great difficulty in the design of the formula of the solvent. Knowledge of the energetics of the solvent-lead iodide (PbI2) adduct allows a quantitative evaluation of the coordination ability of the solvent. Herein, first-principles calculations are performed to explore the interaction of various organic solvents (Fa, AC, DMSO, DMF, GBL, THTO, NMP, and DPSO) with PbI2. Our study establishes the energetics hierarchy with an order of interaction as DPSO > THTO > NMP > DMSO > DMF > GBL. Different from the common notion of forming intimate solvent-Pb bonds, our calculations reveal that DMF and GBL cannot form direct solvent-Pb2+ bonding. Other solvent bases, such as DMSO, THTO, NMP, and DPSO, form direct solvent-Pb bonds, which penetrate through the top iodine plane and possess much stronger adsorption than DMF and GBL. A strong solvent-PbI2 adhesion (i.e., DPSO, NMP, and DMSO), associated with a high coordinating ability, explains low volatility, retarded precipitation of the perovskite solute, and tendency of a large grain size in the experiment. In contrast, weakly coupled solvent-PbI2 adducts (i.e., DMF) induces a fast evaporation of the solvent, accordingly a high nucleation density and small grains of perovskites are observed. For the first time, we reveal the promoted absorption above the iodine vacancy, which implies the need for pre-treatment of PbI2 like vacuum annealing to stabilize solvent-PbI2 adducts. Our work establishes a quantitative evaluation of the strength of the solvent-PbI2 adducts from the atomic scale perspective, which allows the selective engineering of the solvent for high-quality perovskite films.

10.
Front Pharmacol ; 14: 1101063, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37153777

RESUMEN

Background: Apatinib is a novel tyrosine kinase inhibitor used in the treatment of advanced hepatocellular carcinoma (HCC). For decades, sorafenib has been a classic first-line treatment option for patients with HCC. This meta-analysis aimed to assess the efficacy and safety of apatinib versus sorafenib/placebo as first-line treatment for intermediate and advanced primary liver cancer (PLC). Methods: A literature search was performed via PubMed, Web of Science, CENTRAL, Embase, CNKI, VIP, and CBM. Data extraction from databases of other languages is not restricted. The Cochrane risk of bias tool, modified Jadad scale, Newcastle-Ottawa scale (NOS), and non-randomized studies of interventions (ROBINS-I) tool were employed to evaluate methodological qualities in original studies. Influence analysis was applied to assess the reliability of pooled results. Publication bias was evaluated using the funnel plot with Begg's test and Egger's test. Results: Seven studies were included in the systematic review and meta-analysis. Four randomized controlled trials (RCTs) and one clinical controlled trial (CCT) were used for comparing apatinib with placebo, and two retrospective clinical studies (RCSs) were used for comparing apatinib with sorafenib. Apatinib led to higher overall effects in objective response rate (ORR), disease control rate (DCR), and mean survival time (MST) over placebo (RR = 2.03, 95% CI = 1.46-2.81, p < 0.0001, I2 = 0%; RR = 1.17, 95% CI = 1.04-1.33, p = 0.009, I2 = 45.8%; SMD = 2.63; 95% CI = 1.47-3.78, p < 0.0001, I2 = 92.7%, respectively). Compared to sorafenib, apatinib showed no superiority in ORR and DCR but was inferior in the 6-month and 1-year survival rate (RR = 1.99, 95% CI = 0.85-4.65, p = 0.111, I2 = 68.3%; RR = 1.04, 95% CI = 0.73-1.47, p = 0.840, I2 = 0.0%; RR = 0.63, 95% CI = 0.42-0.97, p = 0.036, I2 = 0.0%; RR = 0.47, 95% CI = 0.29-0.79, p < 0.0001, I2 = 0.0%, respectively). Apatinib had similar adverse effects over placebo but possessed a greater incidence rate of proteinuria and hypertension over sorafenib. Conclusion: In the first-line setting, apatinib might be an alternative treatment approach for patients with intermediate and advanced PLC. Sorafenib alone showed a better survival rate within 1 year and a lower incidence rate in hypertension and proteinuria than apatinib monotherapy.

11.
iScience ; 26(5): 106731, 2023 May 19.
Artículo en Inglés | MEDLINE | ID: mdl-37216110

RESUMEN

Recent successful growth of asymmetric transition metal dichalcogenides via accurate manipulation of different chalcogen atoms in top and bottom surfaces demonstrates exotic electronic and chemical properties in such Janus systems. Within the framework of density functional perturbation theory, anharmonic phonon properties of monolayer Janus MoSSe sheet are explored. By considering three-phonons scattering, out-of-plane flexural acoustic (ZA) mode tends to undergo a stronger phonon scattering than transverse acoustic (TA) mode and the longitudinal acoustic (LA) mode with phonon lifetime of ZA (1.0 ps) < LA (23.8 ps) < TA (25.8 ps). This is sharply different from the symmetric MoS2 where flexural ZA mode has the weakest anharmonicity and is least scattered. Moreover, utilizing non-equilibrium Green function method, ballistic thermal conductance at room temperature is found to be around 0.11 nWK-1nm-2, lower than that of MoS2. Our work highlights intriguing phononic properties of such MoSSe Janus layers associated with asymmetric surfaces.

12.
J Phys Condens Matter ; 35(20)2023 Mar 16.
Artículo en Inglés | MEDLINE | ID: mdl-36881922

RESUMEN

Hydrogen as the cleanest energy carrier is a promising alternative renewable resource to fossil fuels. There is an ever-increasing interest in exploring efficient and cost-effective approaches of hydrogen production. Recent experiments have shown that single platinum atom immobilized on the metal vacancies of MXenes allows a high-efficient hydrogen evolution reaction (HER). Here usingab initiocalculations, we design a series of substitutional Pt-doped Tin+ 1CnTx(Tin+ 1CnTx-PtSA) with different thicknesses and terminations (n= 1, 2 and 3, Tx= O, F and OH), and investigate the quantum-confinement effect on the HER catalytic performance. Surprisingly, we reveal a strong thickness effect of the MXene layer on the HER performance. Among the various surface-terminated derivatives, Ti2CF2-PtSAand Ti2CH2O2-PtSAare found to be the best HER catalysts with the change of Gibbs free energy ΔGH*∼ 0 eV, complying with the thermoneutral condition. Theab initiomolecular dynamics simulations reveal that Ti2CF2-PtSAand Ti2CH2O2-PtSApossess a good thermodynamic stability. The present work shows that the HER catalytic activity of the MXene is not solely governed by the local environment of the surface such as Pt single atom. We point out the critical role of thickness control and surface decoration of substrate in achieving a high-performance HER catalytical activity.

13.
Front Pharmacol ; 14: 1118793, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36909155

RESUMEN

Methicillin-resistant Staphylococcus aureus (MRSA) is a drug-resistant bacterium that can cause a range of infections with high morbidity and mortality, including pneumonia, etc. Therefore, development of new drugs or therapeutic strategies against MRSA is urgently needed. Increasing evidence has shown that combining antibiotics with "antibacterial sensitizers" which itself has no effect on MRSA, is highly effective against MRSA. Many studies showed the development of antibacterial sensitizers from natural plants may be a promising strategy against MRSA because of their low side effects, low toxicity and multi-acting target. In our paper, we first reviewed the resistance mechanisms of MRSA including "Resistance to Beta-Lactams", "Resistance to Glycopeptide antibiotics", "Resistance to Macrolides, Aminoglycosides, and Oxazolidinones" etc. Moreover, we summarized the possible targets for antibacterial sensitizers against MRSA. Furthermore, we reviewed the synergy effects of active monomeric compounds from natural plants combined with antibiotics against MRSA and their corresponding mechanisms over the last two decades. This review provides a novel approach to overcome antibiotic resistance in MRSA.

14.
Adv Mater ; 35(25): e2210176, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-36943743

RESUMEN

The power conversion efficiency (PCE) of the state-of-the-art large-area slot-die-coated perovskite solar cells (PSCs) is now over 19%, but issues with their stability persist owing to significant intrinsic point defects and a mass of surface imperfections introduced during the fabrication process. Herein, the utilization of a hydrophobic all-organic salt is reported to modify the top surface of large-area slot-die-coated methylammonium (MA)-free halide perovskite layers. Bearing two molecules, each of which is endowed with anchoring groups capable of exhibiting secondary interactions with the perovskite surfaces, the organic salt acts as a molecular lock by effectively binding to both anion and cation vacancies, substantially enhancing the materials' intrinsic stability against different stimuli. It not only reduces the ingression of external species such as oxygen and moisture, but also suppresses the egress of volatile organic components during the thermal stability testing. The treated PSCs demonstrate efficiency of 19.28% (active area of 58.5 cm2 ) and 17.62% (aperture area of 64 cm2 ) for the corresponding mini-module. More importantly, unencapsulated slot-die-coated mini-modules incorporating the all-organic surface modifier show ≈80% efficiency retention after 7500 h (313 days) of storage under 30% relative humidity (RH). They also remarkably retain more than 90% of the initial efficiency for over 850 h while being measured continuously.

15.
Nanoscale Horiz ; 8(3): 404-411, 2023 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-36723237

RESUMEN

Two-dimensional (2D) materials tend to have the preferable formation of vacancies at the outer surface. Here, contrary to the normal notion, we reveal a type of vacancy that thermodynamically initiates from the interior part of the 2D backbone of germanium selenide (γ-GeSe). Interestingly, the Ge-vacancy (VGe) in the interior part of γ-GeSe possesses the lowest formation energy amongst the various types of defects considered. We also find a low diffusion barrier (1.04 eV) of VGe, which is half of those of sulfur vacancies in MoS2. The facile formation of mobile VGe is rooted in the antibonding coupling of the lone-pair Ge 4s and Se 4p states near the valence band maximum, which also exists in other gamma-phase MX (M = Sn, Ge; X = S, Te). The VGe is accompanied by a shallow acceptor level in the band gap and induces strong infrared light absorption and p-type conductivity. The VGe located in the middle cationic Ge sublattice is well protected by the surface Se layers - a feature that is absent in other atomically thin materials. Our work suggests that the unique well-buried inner VGe, with the potential of forming structurally protected ultrathin conducting filaments, may render the GeSe layer an ideal platform for quantum emitting, memristive, and neuromorphic applications.

16.
Biomacromolecules ; 24(2): 640-651, 2023 02 13.
Artículo en Inglés | MEDLINE | ID: mdl-36689602

RESUMEN

Negatively surface-charged sulfate cellulose nanocrystals (CNCs) are always slowly self-assembled into left-handed cholesteric mesophases. In this work, macroscopic spiral patterns induced by counterclockwise vortex flowing or chiral doping were investigated. Results show that iridescent patterns of the arithmetic spiral, rose spiral, or latitude ripples were generated under the vortex rotation, indicating a severe microphase separation of CNCs. Moreover, the spiral pattern and rotational symmetry were highly correlated to the twisting and flowability of CNCs as well as chiral dopants. Alternatively, the cholesteric pitch and maximum reflective wavelength (λmax) of CNCs were strongly increased by sinistral dopants other than the dextral ones, indicating an enhanced torsion of left-handed CNC mesophases by the dextral dopants. In addition, macroscopic spiral patterns distinctly existed in dextrally doped CNCs owing to a synergistic chiral enhancement. Therefore, the mechanochiral or chemical chiral transition from microscopic twisting to macroscopic spiral provides a potential inspiration for chiral self-organization of biological macromolecules.


Asunto(s)
Celulosa , Nanopartículas , Celulosa/química , Nanopartículas/química
17.
Nat Commun ; 14(1): 411, 2023 Jan 25.
Artículo en Inglés | MEDLINE | ID: mdl-36697404

RESUMEN

Multilayers consisting of alternating soft and hard layers offer enhanced toughness compared to all-hard structures. However, shear instability usually exists in physically sputtered multilayers because of deformation incompatibility among hard and soft layers. Here, we demonstrate that 2D hybrid organic-inorganic perovskites (HOIP) provide an interesting platform to study the stress-strain behavior of hard and soft layers undulating with molecular scale periodicity. We investigate the phonon vibrations and photoluminescence properties of Ruddlesden-Popper perovskites (RPPs) under compression using a diamond anvil cell. The organic spacer due to C4 alkyl chain in RPP buffers compressive stress by tilting (n = 1 RPP) or step-wise rotational isomerism (n = 2 RPP) during compression, where n is the number of inorganic layers. By examining the pressure threshold of the elastic recovery regime across n = 1-4 RPPs, we obtained molecular insights into the relationship between structure and deformation resistance in hybrid organic-inorganic perovskites.

18.
Front Biosci (Landmark Ed) ; 27(11): 313, 2022 11 25.
Artículo en Inglés | MEDLINE | ID: mdl-36472109

RESUMEN

Platelets are small, anucleate cellular fragments, which are produced by megakaryocytes, and play a key role in hemostasis and thrombus formation. The differentiation of megakaryocytes from hematopoietic stem cells in bone marrow and the development of megakaryocytes into platelets is a complex process. Various regulatory factorsin megakaryopoiesis including cytokines, growth factors, transcription factors, and gene expression, are all involved in the process of thrombocytopoiesis and play distinct roles in different stages of megakaryocytes development. In this review, we summarize the current state of knowledge ofmultiple regulatory factors including the TPO/Mpl signaling pathway, transcription factors, RasGTPases family, estrogen, and microRNAs. Altogether, we aimed to discuss more molecular mechanisms of megakaryocytes differentiation and maturation, and possess a better understanding of platelet formation.


Asunto(s)
Megacariocitos , Trombopoyetina , Megacariocitos/metabolismo , Trombopoyetina/genética , Trombopoyetina/metabolismo , Hematopoyesis/genética , Plaquetas/metabolismo , Células Madre Hematopoyéticas , Factores de Transcripción/metabolismo
19.
Nanomaterials (Basel) ; 12(19)2022 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-36234623

RESUMEN

Metal halide perovskites have become a research highlight in the optoelectronic field due to their excellent properties. The perovskite light-emitting diodes (PeLEDs) have achieved great improvement in performance in recent years, and the construction of quasi-2D perovskites by incorporating large-size organic cations is an effective strategy for fabricating efficient PeLEDs. Here, we incorporate the fluorine meta-substituted phenethylammonium bromide (m-FPEABr) into CsPbBr3 to prepare quasi-2D perovskite films for efficient PeLEDs, and study the effect of fluorine substitution on regulating the crystallization kinetics and phase distribution of the quasi-2D perovskites. It is found that m-FPEABr allows the transformation of low-n phases to high-n phases during the annealing process, leading to the suppression of n = 1 phase and increasing higher-n phases with improved crystallinity. The rational phase distribution results in the formation of multiple quantum wells (MQWs) in the m-FPEABr based films. The carrier dynamics study reveals that the resultant MQWs enable rapid energy funneling from low-n phases to emission centers. As a result, the green PeLEDs achieve a peak external quantum efficiency of 16.66% at the luminance of 1279 cd m-2. Our study demonstrates that the fluorinated organic cations would provide a facile and effective approach to developing high-performance PeLEDs.

20.
ChemSusChem ; 15(15): e202200564, 2022 Aug 05.
Artículo en Inglés | MEDLINE | ID: mdl-35680606

RESUMEN

Existence of van der Waals gaps renders two-dimensional (2D) materials ideal passages of lithium for being used as anode materials. However, the requirement of good conductivity significantly limits the choice of 2D candidates. So far, only graphite is satisfying due to its relatively high conductivity. Recently, a new polymorph of layered germanium selenide (γ-GeSe) was proven to be semimetal in its bulk phase with a higher conductivity than graphite while its monolayer behaves semiconducting. In this work, by using first-principles calculations, the possibility was investigated of using this new group-IV monochalcogenide, γ-GeSe, as anode in Li-ion batteries (LIBs). The studies revealed that the Li atom would form an ionic adsorption with adjacent selenium atoms at the hollow site and exist in cationic state (lost 0.89 e to γ-GeSe). Results of climbing image-nudged elastic band showed the diffusion barrier of Li was 0.21 eV in the monolayer limit, which could activate a relatively fast diffusion even at room temperature on the γ-GeSe surface. The calculated theoretical average voltages ranged from 0.071 to 0.015 V at different stoichiometry of Lix GeSe with minor volume variation, suggesting its potential application as anode of LIBs. The predicted moderate binding energy, a low open-circuit voltage (comparable to graphite), and a fast motion of Li suggested that γ-GeSe nanosheet could be chemically exfoliated via Li intercalation and is a promising candidate as the anode material for LIBs.

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